PROJECT SUMMARY/ABSTRACT Recurrent herpetic disease, caused by an immuno-pathological response to herpes simplex virus (HSV-1), is a major cause of infectious blindness in the United States. Although most individuals shed HSV-1 in their tears following reactivation of latent (dormant) virus from the trigeminal ganglia (TG), they never develop recurrent ocular herpetic disease and are asymptomatic (ASYMP). In contrast, a small number of individuals are symptomatic (SYMP), with frequent bouts of recurrent disease. Our long-term goal is to delineate the immune mechanisms that control recurrent herpetic disease, with an eye toward developing a long-lasting antiviral immuno-therapy that successfully prevents or ameliorates recurrent ocular herpes. It has been established that: (1) adaptive immunity, and particularly antiviral CD8+ T cells, protect, in vitro, from HSV-1 reactivation in latently infected TG; and (2) the HSV-1 latency associated transcript (LAT), the only gene that is expressed during latency, restrains the function of antiviral CD8+ T cells. However, key knowledge gaps still remain including: (1) the mechanisms by which CD8+ T cells protect from reactivation, virus shedding in tears, and recurrent disease; and (2) the immune evasion strategies evolved by the virus as a counter-defense against the host?s CD8+ T cells. We recently made four discoveries that serve as the foundation for this proposal: (1) Peripheral blood-derived HSV-specific CD8+ T cells from ASYMP individuals are mostly effector memory (TEM) cell subset, in contrast to mostly central memory (TCM) cell subset in SYMP individuals. (2) Using our novel double transgenic mouse model, expressing Human Leukocyte Antigens HLA-DR and HLA-A*02:01 (HLA Tg mice), multiple recurrences of ocular herpetic disease can be induced by UV-B irradiation, closely mimicking SYMP clinical recurrent herpetic disease. (3) TG-resident CD8+ TRM cells are associated with ASYMP herpes infection of HLA Tg mice. (4) Exhausted (dysfunctional) CD8+ TRM cells in the cornea and TG are associated with SYMP recurrent disease. Building on these preliminary and published findings, our central hypothesis is that interactions between specific subsets of TG- and cornea-resident CD8+ T cells and viral factors determine the development of recurrent herpetic disease. We propose the following Specific Aims: Aim 1: Test the hypothesis that, similar to humans, HSV-specific CD8+ T cells from latently infected ASYMP HLA Tg mice are mostly TEM/TRM, while in SYMP HLA Tg mice (one or more episodes of UV-B induced recurrent disease) they are mostly TCM. Aim 2: Test the hypothesis that therapeutic vaccination with ASYMP CD8+ TEM/TRM cell epitopes, but not with SYMP CD8+ TCM epitopes, will reduce virus reactivation and lessen recurrent herpetic disease in HLA Tg mice. This translational research project, which gathers a multidisciplinary team, addresses the current NEI Audacious Goals Initiative: ?Development of new treatments through small molecules approach to treat eye disease and to restore sight.? Successful completion of this project will lay the foundation toward developing an effective immunotherapeutic intervention to prevent blinding recurrent herpetic disease.